Machine for butt welding of pipes

A machine for the butt welding of pipes of the type including a stationary frame, guides supported by the frame, movable and stationary casings supported on the guides, one or more hydraulic flashing and upsetting cylinders for moving the movable casing along the guides toward and away from the stationary casing and mechanisms with rings and shoes on both of the movable and stationary casings for aligning and clamping the outsides of pipes, the improvement wherein each of said mechanisms comprises a rotatable ring, one or more casing guide surfaces slidably engaging an inner edge of the ring to align the ring for rotation about a machine axis, a plurality of radial slots in the casing distributed around and centered on said axis, a corresponding plurality of shoes movable along said slots toward and away from said axis within said ring, a corresponding plurality of shackles having corresponding first ends pivotally connected to said ring at spaced apart locations therearound and corresponding second ends pivotally connected within the ring to different ones of said shoes so that when the ring is rotated in a first direction about said axis, the shoes are moved along said slots toward said axis and when the ring is rotated in a second, opposite, direction about said axis, the shoes are moved along said slots away from said axis, and a rotating device for rotating said ring alternatively in said first and second directions.